/** Return true, if point is on edge line and no stone is within a
Manhattan distance of 4. */
bool IsEmptyEdge(const GoBoard& bd, SgPoint p)
{
SG_ASSERT (bd.IsEmpty(p));
SG_ASSERT (bd.Line(p) == 1);
if (bd.Num8EmptyNeighbors(p) < 5)
return false;
const SgPoint pUp = p + bd.Up(p);
SG_ASSERT(bd.Line(pUp) == 2);
SG_ASSERT(bd.Pos(pUp) >= 2); // (1,1) goes to (2,2)
if (bd.Num8EmptyNeighbors(pUp) < 8)
return false;
switch (bd.Pos(p))
{
case 1: // (1,1) point
case 2: // (1,2) point
case 3:
return IsEmptyOrInCorner(bd, p, bd.Left(p))
&& IsEmptyOrInCorner(bd, p, bd.Right(p));
// assume in empty corner, 1st line is always
// dominated bymove on 2nd line above
default: // > 3, can test both sides easily
return IsEmpty2x3Box(bd, p + 2*bd.Left(p))
&& IsEmpty2x3Box(bd, p + 2*bd.Right(p))
;
}
}
bool GoEyeUtil::NumberOfMoveToEye(const GoBoard& board, SgBlackWhite color,
SgPoint p, int& number)
{
SG_ASSERT(board.IsEmpty(p));
SgBlackWhite att = SgOppBW(color); // attacker
if ( board.Line(p) == 1) // corner or edge
{
if ( board.Num8Neighbors(p, att) > 0 )
return false;
else
{
number = board.Num8EmptyNeighbors(p);
return true;
}
}
else // in center
{
if ( board.Num8Neighbors(p, att) >= 2 )
return false;
else if ( board.NumNeighbors(p, att) > 0 )
return false;
else // only 0 or 1 attacker point and not in NB4
{
number = board.Num8EmptyNeighbors(p);
return true;
}
}
}
bool GoEyeUtil::IsPossibleEye(const GoBoard& board, SgBlackWhite color,
SgPoint p)
{
bool isPossibleEye = false;
SG_ASSERT(board.GetColor(p) != color);
const SgBlackWhite opp = SgOppBW(color);
if (board.Line(p) == 1) // corner or edge
{
const int nuOwn = (board.Pos(p) == 1) ? 2 : 4;
if ( board.Num8Neighbors(p, color) == nuOwn
&& board.Num8EmptyNeighbors(p) == 1
)
{
isPossibleEye = true;
}
}
else // in center
{
// have all neighbors, and 2 diagonals, and can get a third
if ( board.NumNeighbors(p, color) == 4
&& board.NumDiagonals(p, color) == 2
&& board.NumEmptyDiagonals(p) > 0
)
{
isPossibleEye = true;
}
// have 3 of 4 neighbors, can get the 4th, and have enough diagonals
else if ( board.NumNeighbors(p, color) == 3
&& board.NumNeighbors(p, opp) == 0
&& board.NumDiagonals(p, color) >= 3
)
{
isPossibleEye = true;
}
}
return isPossibleEye;
}
//----------------------------------------------------------------------------
inline bool IsEmpty2x3Box(const GoBoard& bd, SgPoint p)
{
SG_ASSERT (bd.Line(p) == 1);
SG_ASSERT (bd.Pos(p) > 1);
return bd.IsEmpty(p) && bd.Num8EmptyNeighbors(p) == 5;
}
